The present invention relates to a handling device e.g. for moving parts to be assembled or completed along an assembly line. Specifically the device can be employed for moving the parts from one station to the next and positioning them exactly in front of the assembly equipment. Systems of movement between stations along assembly lines are widely used today in industry and in particular in the automobile industry (to which reference is made in this description by way of non-limiting example only).
At each station one or more parts of the body are arranged in the right position and attached to the body. The process is repeated on the necessary number of work stations until all the parts making up the body have been assembled to make up the complete body. Moving the components from one station to the next can be performed by different movement systems. Since the moving time between one station and the next is a non-productive time which must therefore be minimized the speed and accuracy of movement are decisive factors in the choice of movement systems. It is clear that investment and management costs are taken into due account in this choice.
In the course of the years there have been developed many moving systems each of which seeks to give priority to one of the aspects and all seeking the best compromise between performance and costs.
Basically these systems can be divided in three categories, to wit overhead self-movers which move the parts by means of a plurality of vehicles powered individually which run hanging from an overhead rail to transit in sequence above the work stations; `raise and move` systems which move the parts by means of a long multiple apparatus which simultaneously moves all the bodies present in a section (10 to 15 stations) of the assembly line; `skid` systems which move the parts by means of a series of floor conveyors on which move a plurality of sled-like apparatuses termed `skid` on each of which is rested a part to be handled.
In general the skid system displays advantages from the point of view of purchase and management costs while movement time is normally longer than with the other systems. In its simplest form the skid system consists of a series of tables with powered metal rollers on which move the skids. In the course of the years numerous variations were developed on this base tending to improve performance of the system as concerns speed, positioning accuracy and noise level to improve the biotechnology in the work place.
The embodiment which best balances cost, speed, positioning accuracy, quietness etcetera is the double-belt version as described in Italian Utility Model No. 184.610 filed May 6, 1981 in the name of Fata European group S.p.A. In this version on the two sides of the running line there are parallel powered belts for conveying the skid which arrives on the table. The belts run above a continuous supporting table having side shoulders for continuous containment of the belts to prevent lateral slipping. Continuous support appears necessary for supporting the vertical load consisting of the sleds with the belts. Running on an unbroken surface makes unnecessary the use of toothed belts which would be too noisy and which wear out too fast and require large diameter drive pulleys and preloading of the smooth belt to avoid slipping. In the case of the small tapes applied to the skid tables the solution of having the belt slide on an unbroken supporting surface has become generally used because in the prior art it is believed that this solution is the best for reducing noise and facilitating guidance of the belt.
There is a need to further reduce idle times in movement while holding unchanged or improving positioning accuracy in the work stations and noise during moving. In known skid systems it is necessary to use additional centering devices for accurate positioning of the skid within each work station.
The general purpose of the present invention is to overcome the above mentioned drawbacks by making available a skid handling system which would reduce moving time between two successive work stations with positioning accuracy making the employment of additional centering devices for positioning the skid opposite the equipment of the work station not indispensable.